(a) Field of the Invention
The present invention relates generally to antennas and, more particularly, to antennas for receiving or transmitting radiation through a dielectric material.
(b) Description of Related Art
Satellites are commonly used to relay or communicate electronic signals, including audio, video, data, audio-visual, etc. signals, to or from any portion of a large geographical area, such as the continental United States. A satellite-based signal distribution system generally includes an earth station that modulates a carrier frequency with an audio/visual/data signal and then transmits (uplinks) the modulated signal to one or more, for example, geosynchronous satellites. The satellite(s) amplify the received signal, shift the signal to a different carrier frequency band and transmit (downlink) the frequency shifted signal to earth for reception at individual receiving units. Likewise, individual receiving units may transmit a signal, via a satellite, to the base station or to other receiving units.
Many satellite communication systems, including some commercial and military mobile communication systems as well as a direct-to-home satellite system developed by DIRECTV.RTM. (known commercially as DSS.RTM.), use millimeter wave (mmW) carrier frequencies, such as Ku band (ranging from approximately 12 GHz to 18 GHz) to transmit a signal from a satellite to one or more receiver units and/or vise-versa. Other known communication systems use a number of transmitters spaced throughout a geographical region to relay communications signals to and from individual receiver units within the regions.
Still other known communication systems operate in the mmW range above Ku-band and, in some instances, provide free-space point-to-point communication using the 60 GHz carrier frequency range where high signal losses occur. For example, it has been suggested to locate a parabolic dish antenna on an exterior portion of a building to receive a communication signal at, for example, Ku-band, and then to retransmit the communication signal at or near the 60 GHz carrier frequency band to receiving antennas associated with a number of receiving units within the building via transmitting antennas that overhang the roof of the building.
In all of these communication system configurations, it is desirable to use a Ku-band, a 60 GHz, or other receiving/transmitting antenna located on the interior of a building or a mobile unit to receive signals from or to transmit signals to a satellite antenna, a roof-mounted antenna or other antenna. Such an interior-mounted antenna eliminates the necessity of drilling holes in walls of the building, mounting further antennas on the exterior of a building or a mobile unit and/or running cable from each receiving unit to an exterior portion of a building or a mobile unit.
Due to space constraints, a receive/transmitting antenna mounted on the interior of a building or mobile unit should be small and relatively unobtrusive and, preferably, should be able to be mounted directly to, for example, a window to receive or transmit a communication signal through the window. The parabolic dish antennas associated with most communications systems satisfy neither of these criteria.